U.S. patent number 10,834,327 [Application Number 16/361,055] was granted by the patent office on 2020-11-10 for imaging apparatus, method of controlling imaging apparatus, and recording medium.
This patent grant is currently assigned to CANON KABUSHIKI KAISHA. The grantee listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Kenzo Hisa.
United States Patent |
10,834,327 |
Hisa |
November 10, 2020 |
Imaging apparatus, method of controlling imaging apparatus, and
recording medium
Abstract
An imaging apparatus includes an imaging device, an optical
member that adjusts an amount of light of an object image incident
on the imaging device, at least one memory storing a program, and
at least one processor that when executing the program is
configured to adjust transmittance of the optical member, amplify
an image signal output when an image of an object is captured using
the imaging device, and control exposure by changing an exposure
condition including an exposure index.
Inventors: |
Hisa; Kenzo (Inagi,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
N/A |
JP |
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Assignee: |
CANON KABUSHIKI KAISHA (Tokyo,
JP)
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Family
ID: |
1000005176306 |
Appl.
No.: |
16/361,055 |
Filed: |
March 21, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190306397 A1 |
Oct 3, 2019 |
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Foreign Application Priority Data
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Mar 29, 2018 [JP] |
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2018-065510 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N
5/23293 (20130101); H04N 5/2352 (20130101); H04N
5/2355 (20130101); H04N 5/2351 (20130101) |
Current International
Class: |
H04N
5/235 (20060101); H04N 5/232 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2004-289348 |
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Oct 2004 |
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JP |
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2004289348 |
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Oct 2004 |
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JP |
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Primary Examiner: Hsu; Amy R
Attorney, Agent or Firm: Canon U.S.A., Inc. IP Division
Claims
What is claimed is:
1. An imaging apparatus, comprising: an imaging device; an optical
member configured to adjust an amount of light of an object image
incident on the imaging device; at least one memory storing a
program; and at least one processor that when executing the program
is configured to: adjust transmittance of the optical member;
amplify an image signal output when an image of an object is
captured using the imaging device; and control exposure by changing
an exposure condition including an exposure index, wherein a value
of the exposure index is settable by a user from predetermined
discrete values, wherein the exposure condition includes an
aperture value and an accumulation time which are different from
the exposure index, and wherein a combination of an amplification
factor of the image signal to be used in amplifying the image
signal and the transmittance of the optical member is predetermined
for each exposure index settable by the user.
2. The imaging apparatus according to claim 1, further comprising:
a storage unit configured to store first information relating to
the exposure index, wherein the first information includes a
plurality of combinations of the transmittance of the optical
member and the amplification factor of the image signal in a case
where the exposure index is a first value.
3. The imaging apparatus according to claim 2, wherein, in the case
where the exposure index is the first value, the first information
includes a first combination in which the transmittance of the
optical member is a second value and the amplification factor of
the image signal is a third value, and a second combination in
which the transmittance of the optical member is a fourth value and
the amplification factor of the image signal is a fifth value,
wherein the second value of the transmittance of the optical member
is larger than the fourth value, and wherein the third value of the
amplification factor of the image signal is smaller than the fifth
value.
4. The imaging apparatus according to claim 2, wherein the at least
one processor is further configured to control display on a display
unit, and wherein display is controlled such that at least
information relating to the first value out of the first
information relating to the exposure index is displayed on the
display unit.
5. The imaging apparatus according to claim 2, wherein the first
information includes two or more combinations of different
transmittance of the optical member, a different amplification
factor of the imaging signal, and a same exposure index.
6. The imaging apparatus according to claim 4, wherein the at least
one processor is further configured to perform gamma correction on
the image signal, and herein first signal amplification is
performed for amplifying the image signal before the gamma
correction is performed, and second signal amplification is
performed for applying gamma correction characteristics of a
similar shape to change a dynamic range and to amplify the image
signal.
7. The imaging apparatus according to claim 6, wherein display is
controlled such that one or more of information relating to an
amplification amount for the first signal amplification or
information relating to an amplification amount for the second
signal amplification is displayed on the display unit.
8. The imaging apparatus according to claim 2, wherein, as a
setting for capturing an image of an object by the imaging
apparatus, a first setting in which importance is placed on a
dynamic range and a second setting different from the first setting
are settable, and wherein, in the first information, the
transmittance of the optical member is smaller and the
amplification factor of the image signal is larger when a
predetermined exposure index is set in a case where the first
setting is selected than in a case where the second setting is
selected.
9. The imaging apparatus according to claim 8, wherein the second
setting is a setting in which importance is placed on reduction of
a noise amount in the image signal.
10. The imaging apparatus according to claim 8, wherein the dynamic
range is settable as the setting in the imaging of the object by
the imaging apparatus, and wherein the transmittance of the optical
member is changed in a case where an amplification amount changed
in the second signal amplification with respect to a change of the
exposure index becomes an amount corresponding to the set dynamic
range.
11. The imaging apparatus according to claim 2, wherein the
amplification factor of the image signal is controlled by gamma
correction to be performed on the image signal and gain adjustment
of the image signal, and wherein the amplification factor of the
image signal is changed by the gamma correction in preference to a
change of the amplification factor of the image signal by the gain
adjustment.
12. A method of controlling an imaging apparatus that includes an
imaging device and an optical member configured to adjust an amount
of light of an object image incident on the imaging device, the
method comprising: adjusting transmittance of the optical member;
amplifying an image signal output when an image of an object is
captured with use of the imaging device; and controlling exposure
by changing an exposure condition including an exposure index,
wherein a value of the exposure index is settable by a user from
predetermined discrete values, wherein the exposure condition
includes an aperture value and an accumulation time which are
different from the exposure index, and wherein a combination of an
amplification factor of the image signal and the transmittance of
the optical member is predetermined for each exposure index
settable by the user.
13. A non-transitory computer-readable recording medium storing a
program for causing a processor to execute a method of controlling
an imaging apparatus that includes an imaging device and an optical
member configured to adjust an amount of light of an object image
incident on the imaging device, the control method comprising:
adjusting transmittance of the optical member; amplifying an image
signal output when an image of an object is captured with use of
the imaging device; and controlling exposure by changing an
exposure condition including an exposure index, wherein a value of
the exposure index is settable by a user from predetermined
discrete values, wherein the exposure condition includes an
aperture value and an accumulation time which are different from
the exposure index, and wherein a combination of an amplification
factor of the image signal and the transmittance of the optical
member is predetermined for each exposure index settable by the
user.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present disclosure relates to exposure control of an imaging
apparatus, and in particular to an imaging apparatus that can
change an exposure index, a method of controlling the imaging
apparatus, and a recording medium.
Description of the Related Art
In recent years, an imaging apparatus such as a video camera has
included a function to control exposure during and after imaging of
an object as control to change brightness of image data acquired by
the imaging of the object. To control the exposure, exposure
conditions, such as an aperture diameter of a diaphragm, light
transmittance of an optical filter such as a neutral density (ND)
filter, a charge accumulation time of an imaging device, and an
amplification factor of an image signal are commonly changed. For
simplification of description, in the following description, the
exposure conditions are referred to as diaphragm, transmittance of
ND filter, accumulation time, and amplification factor. These
exposure conditions are optionally changed by a user's manual
operation, are changed by automatic control by an imaging
apparatus, or are changed by a combination of partial manual
operation by the user and the automatic control by the imaging
apparatus.
A system that converts the exposure conditions into additive system
of photographic exposure (APEX) units and thereby generally
controls the exposure in order to simplify exposure control has
been well-known. The proper exposure conditions corresponding to
luminance of the object are settable by total adjustment of the
diaphragm, the accumulation time (shutter speed), and the
amplification factor (imaging sensitivity) based on the luminance
of the object. A depth of field is changed when the diaphragm is
changed, and smoothness of a moving image is changed when the
accumulation time is changed. It has been desired to control the
changes of both of the transmittance of the ND filter and the
amplification factor that do not influence the depth of field and
the smoothness of the moving image in conjunction with each other.
Japanese Patent Application Laid-Open No. 2004-289348 discusses a
technology that sequentially changes the light transmittance of the
ND filter, sensitivity of the imaging device, and a gain of an
image signal processing apparatus without changing the diaphragm as
much as possible, thereby performing automatic sensitivity
adjustment.
SUMMARY OF THE INVENTION
According to an aspect of the present disclosure, an imaging
apparatus includes an imaging device, an optical member configured
to adjust an amount of light of an object image incident on the
imaging device, at least one memory storing a program, and at least
one processor that when executing the program is configured to
adjust transmittance of the optical member, amplify an image signal
output when an image of an object is captured using the imaging
device, and control exposure by changing an exposure condition
including an exposure index. A value of the exposure index is
settable by a user from predetermined discrete values. A
combination of an amplification factor of the image signal to be
used in amplifying the image signal and the transmittance of the
optical member is predetermined for each exposure index settable by
the user.
Further features of the present disclosure will become apparent
from the following description of exemplary embodiments with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an external view illustrating an imaging apparatus
according to a first exemplary embodiment of the present
disclosure.
FIG. 2 is a block diagram illustrating an internal configuration of
the imaging apparatus according to the first exemplary embodiment
of the present disclosure.
FIG. 3 is a flowchart illustrating processing to determine
transmittance of a neutral density (ND) filter, a gain, and gamma
correction characteristics according to the first exemplary
embodiment of the present disclosure.
FIG. 4 is a diagram illustrating a combination of the transmittance
of the ND filter and a signal amplification factor according to the
first exemplary embodiment of the present disclosure.
FIG. 5 is a diagram illustrating a combination of the gain and a
gamma corresponding to the amplification factor according to the
first exemplary embodiment of the present disclosure.
FIG. 6 is a diagram illustrating the gamma correction
characteristics according to the first exemplary embodiment of the
present disclosure.
FIG. 7 is a flowchart relating to display control of exposure
conditions according to a second exemplary embodiment of the
present disclosure.
FIGS. 8A to 8E are diagrams each illustrating information displayed
by display control processing according to the second exemplary
embodiment of the present disclosure.
FIG. 9 is a flowchart illustrating processing to determine
transmittance of an ND filter, a gain, and gamma correction
characteristics according to a third exemplary embodiment of the
present disclosure.
FIG. 10 is a diagram illustrating a combination of the
transmittance of the ND filter and an amplification factor
corresponding to a dynamic (D) range according to the third
exemplary embodiment of the present disclosure.
DESCRIPTION OF THE EMBODIMENTS
Embodiments of the present disclosure are described in detail with
reference to accompanying drawings. FIG. 1 is an external view
illustrating an imaging apparatus 100 according to a first
exemplary embodiment of the present disclosure. In the present
exemplary embodiment, a case where the imaging apparatus 100 is a
digital video camera is illustrated. The imaging apparatus 100
includes a digital camera, a network camera for monitoring, and a
portable device including a camera function such as a
smartphone.
In FIG. 1, a display unit 28 displays an image and various kinds of
information. A recording switch 61 is an operation unit to provide
an imaging instruction. A mode selection switch (not illustrated)
is an operation unit to select one of various kinds of modes. An
operation unit 70 includes operation members such as various kinds
of buttons and a cross key to receive various kinds of operation
from a user. A power switch (not illustrated because being disposed
on opposite surface) switches power-on and power-off. A connector
112 is a connecter between a power connection cable and the imaging
apparatus 100. A recording medium slot 201 stores a recording
medium 200 (not illustrated) such as a memory card and a hard disk.
The recording medium 200 stored in the recording medium slot 201 is
communicable with the imaging apparatus 100.
FIG. 2 is a block diagram illustrating an internal configuration of
the imaging apparatus 100 according to the first exemplary
embodiment of the present disclosure. In FIG. 2, an imaging lens
103 is a lens group including a zoom lens, a focus lens, and a
shift lens, and forms an image of an object. A diaphragm 101 is
used to adjust a light amount. A neutral density (ND) filter 104 is
an optical member to adjust (reduce) an amount of light incident on
an imaging device 22a provided in an imaging unit 22 to be
described below. In the present exemplary embodiment, a turret ND
filter including four filters different in density is provided. The
imaging unit 22 includes the imaging device 22a. The imaging device
22a includes a charge-storage solid-state imaging device such as a
charge-coupled device (CCD) and a complementary metal-oxide
semiconductor (CMOS) device that convert an optical image into an
electric signal. The imaging unit 22 includes a function of
controlling an accumulation time of the imaging device 22a by an
electronic shutter, a function of changing an analog gain, a
function of changing a readout speed, etc. An analog-to-digital
(A/D) converter 23 is used to convert an analog signal output from
the imaging unit 22 into a digital signal. A barrier 102 covers an
imaging system including the imaging lens 103 of the imaging
apparatus 100, thereby preventing stains and damage on the imaging
system including the imaging lens 103, the diaphragm 101, and the
imaging unit 22.
An image processing unit 24 performs processing on data from the
A/D converter 23 or data from a memory control unit 15. The
processing includes predetermined pixel interpolation processing,
resize processing such as reduction processing, color conversion
processing, gamma correction processing, and processing to add a
digital gain. The imaging unit 22 and the image processing unit 24
described above correspond to a signal amplification unit that
amplifies the analog gain and the digital gain in the present
exemplary embodiment, change of an amplification factor of each of
the analog gain and the digital gain is instructed by a system
control unit 50 that functions as an amplification factor changing
unit. The imaging unit 22 and the image processing unit 24 may also
serve as the amplification factor changing unit.
The image processing unit 24 performs predetermined calculation
processing with use of captured image data, and transmits a
calculation result to the system control unit 50. The system
control unit 50 performs exposure control, ranging control, white
balance control, etc., based on the transmitted calculation result.
As a result, autofocus (AF) processing, automatic exposure (AE)
processing, automatic white balance (AWB) processing are performed.
The system control unit 50 operates the shift lens of the imaging
lens 103 in response to motion and attitude change of the imaging
apparatus 100 caused by hand shake detected by a gyro 40, or the
image processing unit 24 shifts an image, so that image blur is to
be corrected.
Data output from the A/D converter 23 is written in a memory 32 via
the image processing unit 24 and the memory control unit 15, or via
the memory control unit 15. The memory 32 stores image data that
has been captured by the imaging unit 22 and converted into digital
data by the A/D converter 23, and image data to be displayed on the
display unit 28. The memory 32 includes a sufficient memory
capacity to store image signals and other various kinds of data.
For example, the memory 32 includes a sufficient memory capacity to
store a moving image and sound for a predetermined time.
The memory 32 also serves as an image display memory (video
memory). A digital-to-analog (D/A) converter 13 converts image
display data stored in the memory 32 into an analog signal, and
supplies the analog signal to the display unit 28. The display
image data thus written in the memory 32 is displayed on the
display unit 28 via the D/A converter 13. The display unit 28
performs display corresponding to the analog signal supplied from
the D/A converter 13 on a display device such as a liquid crystal
display (LCD). The D/A converter 13 converts the digital signal
that has been A/D-converted by the A/D converter 23 and accumulated
in the memory 32, into an analog signal, and the analog signal is
consecutively transferred to and displayed on the display unit 28.
As a result, an electronic viewfinder is achieved and live image
display is performed.
A nonvolatile memory 56 is an electrically erasable/writable
memory, and for example, an electrically erasable programmable
read-only memory (EEPROM) is used. The nonvolatile memory 56 stores
constants, programs, etc. for operation of the system control unit
50. The programs are programs to execute processing illustrated in
flowcharts to be described below.
The system control unit 50 is a control unit including a central
processing unit (CPU) such as a microprocessor that totally
controls the imaging apparatus 100 as a whole. The system control
unit 50 executes the programs recorded in the above-described
nonvolatile memory 56 to execute various processing described below
in the present exemplary embodiment. A random access memory (RAM)
is used for a system memory 52. The constants and variables for
operation of the system control unit 50, the programs read from the
nonvolatile memory 56, etc. are executed in the system memory 52.
The system control unit 50 also controls the memory 32, the D/A
converter 13, the display unit 28, etc. to perform display
control.
A system timer 53 is a clocking unit that clocks a time used for
various kinds of control and clocks a time of a built-in clock. The
mode selection switch 60, the recording switch 61, and the
operation unit 70 are operation units to provide various kinds of
operation instructions to the system control unit 50.
The mode selection switch 60 switches an operation mode of the
system control unit 50 to any of a moving image recording mode, a
still image recording mode, a reproduction mode, etc. Modes
included in the moving image recording mode and the still image
recording mode include an automatic imaging mode, an automatic
scene determination mode, a manual mode, various kinds of scene
modes in which imaging setting is performed depending on a captured
scene, a program AE mode, and a custom mode. The operation mode can
be directly switched to any of these modes included in the moving
image recording mode by operation of the mode selection switch 60.
Alternatively, after the operation mode is switched to the moving
image recording mode by the mode selection switch 60, the operation
mode may be switched to any of these modes included in the moving
image recording mode by the other operation member. The recording
switch 61 switches a state between an imaging standby state and an
imaging state. When the recording switch 61 is turned on, the
system control unit 50 starts a series of operation from reading of
the signal from the imaging unit 22 to writing of moving image data
in the recording medium 200.
When various function icons displayed on the display unit 28 are
selected and operated, the operation members of the operation unit
70 are appropriately assigned with functions for respective scenes
and operate as various kinds of function buttons. Examples of the
function buttons include an end button, a return button, an image
feeding button, a jump button, an iris refining button, and an
attribute change button. For example, when a menu button is
pressed, a menu screen enabling various kinds of settings is
displayed on the display unit 28. A user can intuitively perform
various kinds of settings with use of the menu screen displayed on
the display unit 28, the cross key in vertical and lateral
directions, and a SET button.
A power supply control unit 80 includes a battery detection
circuit, a direct current-direct current (DC-DC) converter, and a
switch circuit that switches a block to be energized, and detects
presence/absence of attachment of a battery, a kind of the battery,
and a remaining battery level. The power supply control unit 80
controls the DC-DC converter based on results of the detection and
an instruction from the system control unit 50, and supplies a
necessary voltage to each of the units including the recording
medium 200 for a necessary period.
A power supply unit 30 includes a primary battery such as an alkali
battery and a lithium battery, a secondary battery such as a
nickel-cadmium (NiCd) battery, a nickel metal hydride (NiMH)
battery, and a lithium (Li) ion battery, or an alternating-current
(AC) adaptor. A recording medium interface (I/F) 18 is an interface
with the recording medium 200 such as a memory card and a hard
disk. The recording medium 200 is a recording medium such as a
memory card to record a captured image, and includes a
semiconductor memory and a magnetic disc.
The imaging device 22a used in the present exemplary embodiment
provides a dynamic range (D range) of the imaging apparatus 100 of
200% in a case where the transmittance of the ND filter 104 is 100%
and an exposure index (EI) is 100. In other words, when proper
exposure in additive system of photographic exposure (APEX) units
is 20% with respect to the maximum value (200%) of the input signal
in the case where the transmittance of the ND filter 104 is 100%
and the exposure index EI is 100, the output signal is saturated
when the input signal is 10 times (200%) the proper exposure. The
exposure condition becomes brighter as the exposure index EI is
increased. For example, when the exposure index EI is 200, the
exposure condition is brighter by one stage than the exposure
condition when the exposure index EI is 100, and when the exposure
index EI is 400, the exposure condition is brighter by two stages
than the exposure condition when the exposure index EI is 100. It
is premised that a value of the exposure index EI is settable by a
user from predetermined discrete values stored in the imaging
apparatus 100.
It is premised that, when the exposure is proper, in APEX units, Av
(aperture value)+Tv (accumulation time (shutter speed))=Sv
(sensitivity)+Bv (brightness of object) is established. The
above-described D range of the imaging apparatus 100 indicates a
width of brightness at which the imaging apparatus 100 can obtain
an unsaturated image by capturing an image of the object. In the
present exemplary embodiment, it is assumed that the D range of a
gamma curve (hereinafter, simply referred to as gamma), indicating
input-output characteristics of the output signal to the input
signal that is output from the imaging device 22a and includes the
amplified analog gain and the amplified digital gain, is 1600%.
Processing to determine the transmittance of the ND filter 104, the
gain, and the gamma correction characteristics according to the
present exemplary embodiment is described with reference to FIG. 3.
FIG. 3 is a flowchart illustrating the processing to determine the
transmittance of the ND filter 104, the gain, and the gamma
correction characteristics according to the present exemplary
embodiment of the present disclosure. The flowchart illustrated in
FIG. 3 is started when the imaging apparatus 100 is turned on or
the imaging mode is changed, or at optional timing based on manual
operation by the user.
As illustrated in FIG. 3, in step S301, the system control unit 50
determines whether the current setting of the imaging apparatus 100
is a D-range-oriented setting. The D-range-oriented setting is a
setting for setting various kinds of imaging conditions in order to
capture an image of the object while maintaining the D range as
wide as possible with respect to the change of the exposure index
EI. In the imaging apparatus 100, the D-range-oriented setting may
be settable as one imaging mode. In a case where the
D-range-oriented setting is not selected (i.e., in case where a
signal-to-noise (S/N)-oriented setting is selected), the D range is
narrowed but reduction of an S/N ratio that indicates a ratio of
the signal to a noise amount can be suppressed in the image signal
obtained by capturing the image of the object.
The D-range-oriented setting and the S/N-oriented setting are
previously selectable by the user. For example, in the imaging
apparatus 100, the user may optionally select the setting as one of
selection items in the menu of the imaging apparatus 100.
In a case where the D-range-oriented setting is selected in step
S301 (YES in step S301), the system control unit 50 selects a
D-range-oriented combination (allocation) of the transmittance of
the ND filter 104 and the amplification factor in step S302. In a
case where the D-range-oriented setting is not selected in step
S301 (NO in step S301), the system control unit 50 selects an
S/N-oriented combination (allocation) of the transmittance of the
ND filter 104 and the amplification factor in step S303.
FIG. 4 is a diagram illustrating combination of the transmittance
of the ND filter 104 and the signal amplification factor according
to the present exemplary embodiment of the present disclosure. In
the present exemplary embodiment, relationships as illustrated in
FIG. 4 are adopted as the combinations of the transmittance of the
ND filter 104 and the amplification factor with respect to each
exposure index (EI).
In FIG. 4, the transmittance of the ND filter 104 is represented by
stops, and 0 stop, 1 stop, 2 stops, and 3 stops correspond to the
transmittance of the ND filter 104 of 100%, 50%, 25%, and 12.5%,
respectively. In other words, when the transmittance of the ND
filter 104 is 3 stops, an amount of light incident on the imaging
device 22a is reduced to 1/8 by the ND filter 104 as compared with
a state where the light amount is not reduced. The amplification
factor is represented by a magnification to amplify the signal, and
.times.2 indicates two times the signal, and .times.4 indicates
four times the signal. The amplification may be performed on the
analog gain or the digital gain, and the amplification factor
indicates at least an amplification factor of the signal amplified
before the gamma curve is applied to the input signal by the gamma
correction circuit.
As illustrated in FIG. 4, in the case where the D-range-oriented
setting is selected, the amplification factor is increased in
preference to increase of the transmittance of the ND filter 104
(i.e., decrease of light reduction amount), based on the increase
of the exposure index EI. At this time, the D range reaches the
maximum D range at a predetermined amplification factor. Therefore,
even if the amplification factor is further increased, the D range
is not increased. Accordingly, priority is given to change of the
transmittance of the ND filter 104 in a state where the
amplification factor is increased to the predetermined
amplification factor, and the amplification factor is again
increased after the transmittance reaches the maximum
transmittance. The relationship between the amplification factor
and the D range is described below.
In contrast, as illustrated in FIG. 4, in the case where the
S/N-oriented setting is selected, the transmittance of the ND
filter 104 is increased in preference to increase of the
amplification factor, based on the increase of the exposure index
EI. In this case, the amplification factor of the signal is
increased after the transmittance of the ND filter 104 reaches the
maximum transmittance (0 stop) based on the increase of the
exposure index EI.
When the D-range-oriented setting and the S/N-oriented setting
described above are compared, in the imaging apparatus 100
according to the present exemplary embodiment, the amplification
factor of the signal in the D-range-oriented setting is larger than
the amplification factor of the signal in the S/N-oriented setting
at each exposure index EI within the range of 25 to 400. In the
imaging apparatus 100 according to the present exemplary
embodiment, the transmittance of the ND filter 104 in the
S/N-oriented setting is larger than the transmittance of the ND
filter 104 in the D-range-oriented setting at each exposure index
EI within the range of 25 to 400.
As illustrated in FIG. 3, in step S304, the system control unit 50
determines the transmittance of the ND filter 104 and the
amplification factor based on the selection result in step S302 or
S303. In the present exemplary embodiment, for example, a
configuration is described in which the exposure index EI is set by
the user as one of exposure conditions (exposure parameters)
optionally settable by the user, just like the values Av and Tv.
However, the configuration is not limited thereto. For example, the
system control unit 50, etc. may determine the transmittance of the
ND filter 104 and the amplification factor based on the state
(whether D-range-oriented setting is selected) previously selected
by the user when the system control unit 50 automatically sets the
most proper exposure index EI corresponding to luminance of the
object.
In step S305, the system control unit 50 determines the gain and
the gamma correction characteristics based on the amplification
factor determined in step S304. FIG. 5 is a diagram illustrating
the combination of the gain and the gamma correction
characteristics based on the amplification factor according to the
present exemplary embodiment of the present disclosure. As
illustrated in FIG. 5, the gain indicates an amount of
amplification of the analog gain or the digital gain in the imaging
unit 22 executed before the gamma curve is applied to the input
signal by the image processing unit 24. A unit of the gamma
correction characteristics is dB. It is assumed that exposure
becomes brighter by one stage in APEX units every time the gain is
increased by 6 dB. As illustrated in FIG. 5, the gamma correction
characteristics are represented by the D range that indicates a
shape of the gamma curve. When the D range is doubled, the
brightness is also doubled. The relationship between the gamma
correction characteristics and the D range is described below.
The imaging device 22a according to the present exemplary
embodiment provides the D range of 200% when the exposure index EI
is 100. Therefore, gamma correction characteristics of 200% is set
when the amplification factor is one time. Accordingly, when the
amplification factor is increased, the gamma correction
characteristics are firstly changed, and then the D range is
expanded. More specifically, when the gamma correction
characteristics are changed to 400%, 800%, and 1600%, the
amplification factor become two times, four times, and eight times,
respectively. In the present exemplary embodiment, for example, in
the case of the gamma correction characteristics at which an upper
limit of the D range is 1600%, when the amplification factor
exceeds eight times, the D range is fixed to 1600%, and the gain is
increased along with the subsequent increase of the amplification
factor. When the gain is increased, the exposure becomes brighter
in response to an increase of the gamma input signal, but the D
range itself is not changed. In other words, the D range
corresponding to the amplification factor of one time, two times,
four times, and eight times (including more than eight times)
illustrated in FIG. 4 are 200%, 400%, 800%, and 1600%,
respectively. Accordingly, in the imaging apparatus 100 according
to the present exemplary embodiment, the D range is wider when the
D-range-oriented setting is selected than when the S/N-oriented
setting is selected, in a case where the exposure index EI is
within the range of 25 to 400.
The relationship between the gamma correction characteristics and
the D range is described with reference to FIG. 6. FIG. 6 is a
diagram illustrating the gamma correction characteristics according
to the present exemplary embodiment of the present disclosure, and
a lateral axis indicates an input and a vertical axis indicates an
output. More specifically, the lateral axis in FIG. 6 indicates an
input code value of the gamma correction circuit, and the vertical
axis indicates an output code value of the gamma correction
circuit. The code value depends on the circuit. When the data unit
is 10 bits, the code value is a value in a range of 0 to 1023. When
the data unit is 12 bits, the code value is a value in a range of 0
to 4096. A curve 601 illustrated in FIG. 6 indicates the gamma
correction characteristics of 1600%, a curve 602 indicates the
gamma correction characteristics of 800%, a curve 603 indicates the
gamma correction characteristics of 400%, and a curve 604 indicates
the gamma correction characteristics of 200%. The curve 601
indicates the gamma correction characteristics in which the output
signal becomes the maximum value Y max when the input signal is the
maximum value X max. Therefore, even if the input signal that has
the D range larger than 1600% is generated, the output signal does
not become larger than the maximum value Y max, and the signal
having the D range of 1600% or more cannot be represented while
proper brightness is maintained. The curve 602 has a similar shape
half-sized in the input direction to the curve 601. For example,
the output value is Y1 when the input value is X max/2 in the curve
601, whereas the output value is Y1 even when the input value is X
max in the curve 602. The curve 603 also has a similar shape
half-sized in the input direction to the curve 602, and the curve
604 also has a similar shape half-sized in the input direction to
the curve 603. Accordingly, when the gamma correction
characteristics are changed from the curve 602 (800%) to the curve
601 (1600%), the brightness of the output value to the input value
becomes brighter by one stage. Therefore, for example, the gamma
correction characteristics indicated by the curve 601 make the
brightness of the object darker by one stage. Alternatively, the
brightness of the object by the gamma correction characteristics
indicated by the curve 601 is equivalent to the brightness of the
object by the gamma correction characteristics indicated by the
curve 602 in a case where the aperture value or the accumulation
time (shutter speed) is lowered by one stage. In other words, by
the gamma correction characteristics indicated by the curve 601,
the signal of up to the output value Y max can be output and the D
range can be increased.
In the above-described exemplary embodiment, the example in which
the gamma correction characteristics are changed to amplify the
signal has been described. However, configuration is not limited
thereto. The D range may be fixed to 1600%, and the amplification
factor of the signal may be adjusted when the digital gain is
adjusted before the gamma correction characteristics are applied.
In this case, the signal can be reduced to 1/8 when the D range is
200%, the signal can be reduced to 1/4 when the D range is 400%,
and the signal can be reduced to 1/2 when the D range is 800%. In
this case, however, gradation property may be impaired depending on
the bit count of the input signal and the output signal because the
input signal is reduced at the time when the gamma correction
characteristics are applied.
In step S306, the system control unit 50 changes the transmittance
of the ND filter, the gain, and the gamma correction
characteristics to the respective values determined in steps S301
to S305. The system control unit 50 controls the ND filter 104, the
imaging unit 22, and the image processing unit 24 in order to
actually adjust the transmittance of the ND filter 104, the gain,
and the gamma correction characteristics to the respective
determined values.
In the present exemplary embodiment, the allocation of the gain and
the gamma correction characteristics corresponding to the
amplification factor is uniformized as illustrated in FIG. 5.
However, the allocation is not limited thereto. For example, in the
case where the S/N-oriented setting is selected, the gain to two
times of the amplification factor may be set to 6 dB and the D
range in the gamma correction characteristics may be set to 200%.
In this configuration, the D range becomes 200% also in the case
where the amplification factor is two times. Therefore, the D range
can be set to 200% when the exposure index EI is 12 to 200. In
other words, as the configuration of the present exemplary
embodiment, a configuration is adoptable in which the range of the
exposure index EI with the wide D range becomes wider when the
D-range-oriented setting is set than when the S/N-oriented setting
is set.
As described above, when the configuration of the imaging apparatus
according to the present exemplary embodiment is adopted, it is
possible to change the transmittance of the ND filter and the
amplification factor in conjunction with each other based on the
setting of the exposure index EI by the user, by controlling the
transmittance of the ND filter, the gain, and the gamma correction
characteristics. Further, in a case where the D-range-oriented
setting is selected, the imaging is performable with the wide D
range within the specific EI range by decreasing the transmittance
of the ND filter as much as possible and increasing the
amplification factor even when the exposure index EI is the same.
This configuration makes it possible to set the various kinds of
imaging conditions to acquire an image with quality reflecting
intention of the user while preventing operability from being
complicated when the transmittance of the ND filter and the
amplification factor of the signal are changed in conjunction with
each other in response to operation by the user.
A second exemplary embodiment is described. In the above-described
first exemplary embodiment, the transmittance of the ND filter and
the amplification factor are comprehensively represented by the
exposure index EI, and the configuration has been described in
which the combination (allocation) of the transmittance of the ND
filter and the amplification factor is changed even at the same
exposure index EI based on whether the D-range-oriented setting is
selected. It is, however, difficult for the user to know the
accurate state of the transmittance of the ND filter and the
amplification factor from simple display of the exposure index EI.
Therefore, there is an instance that the user has difficulty in
realizing a change of the image quality corresponding to the gain,
the gamma correction characteristics, and the transmittance of the
ND filter. Accordingly, in the present exemplary embodiment, a
method of displaying the exposure conditions on the display unit
when the transmittance of the ND filter and the amplification
factor are changed based on the exposure index EI is described.
Description of a configuration of the imaging apparatus according
to the present exemplary embodiment is omitted because the
configuration is substantially the same as the configuration of the
above-described first exemplary embodiment, and description is
given with the same reference numerals.
FIG. 7 is a flowchart relating to display control of the exposure
conditions according to the present exemplary embodiment of the
present disclosure. The flowchart illustrated in FIG. 7 is started
when the imaging apparatus 100 is turned on or at optional timing
based on manual operation by the user, and the display is performed
on the display unit 28, etc. The flowchart illustrated in FIG. 7 is
not limited to the display control of the display unit 28, and is
applicable to display control of a display unit (e.g., display
apparatus externally connected to imaging apparatus 100) other than
the display unit 28.
As illustrated in FIG. 7, after the display control processing is
started, the system control unit 50 displays (instructs display of)
the exposure index EI on the display unit in step S701. It is
assumed that the exposure index EI is previously determined in the
configuration described in the first exemplary embodiment.
In step S702, the system control unit 50 determines whether display
of information relating to the combination of the transmittance of
the ND filter and the amplification factor based on the exposure
index EI has been selected. As the information relating to the
combination, a percentage of each of the transmittance of the ND
filter and the amplification factor may be displayed. In the
present exemplary embodiment, the information indicating the actual
transmittance of the ND filter and the actual amplification factor
is displayed. Presence/absence of the display of the information
relating to the combination is optionally settable by the user in
the menu screen, etc.
The information relating to the combination may be automatically
displayed by determination of the system control unit 50. For
example, in a case where a plurality of combinations of the
transmittance of the ND filter and the amplification factor is
included (present) with respect to the same exposure index EI, the
display may be automatically performed. As with the above-described
first exemplary embodiment, in a case where any of the exposure
index EI of 25 to 400 with the different transmittance of the ND
filter and the different amplification factor is set depending on
whether the D-range-oriented setting or the S/N-oriented setting is
selected, the display may be automatically performed.
In a case where the system control unit 50 determines in step S702
that the display of the information relating to the combination has
not been selected (NO in step S702), only the exposure index EI is
displayed and the transmittance of the ND filter and the
amplification factor are not displayed. In a case where the system
control unit 50 determines in step S702 that the display of the
information relating to the combination has been selected (YES in
step S702), information relating to the transmittance of the ND
filter is displayed in step S703.
In step S704, the system control unit 50 determines whether the
display of information relating to a total amplification factor has
been selected. The information relating to the total amplification
factor is information indicating a total amplification factor of
the gain and the gamma. As with the above-described information
relating to the combination, the information relating to the total
amplification factor is also optionally settable by the user.
In a case where the system control unit 50 determines in step S704
that the display of the information relating to the total
amplification factor has been selected (YES in step S704), the
information relating to the total amplification factor is displayed
in step S705. In a case where the system control unit 50 determines
in step S704 that the display of the information relating to the
total amplification factor has not been selected (NO in step S704),
information relating to each of the gain and the D range is
displayed in step S706.
FIGS. 8A to 8E are diagrams each illustrating the information
displayed by the display control processing according to the
present exemplary embodiment of the present disclosure. FIG. 8A
illustrates a case where only the exposure index EI is displayed
(NO in step S702). FIGS. 8B and 8C each illustrate a case where the
information relating to the combination and the information
relating to the total amplification factor are displayed. In FIG.
8B, the exposure index EI 100 when the D-range-oriented setting is
selected is illustrated. In FIG. 8C, the exposure index EI 100 when
the S/N-oriented setting is selected is illustrated. FIGS. 8D and
8E each illustrate a case where the information relating to the
combination and the information relating to each of the gain and
the D range are displayed. In FIG. 8D, the exposure index EI 100
when the D-range-oriented setting is selected is illustrated. In
FIG. 8E, the exposure index EI 100 when the S/N-oriented setting is
selected is illustrated.
For example, when FIG. 8D and FIG. 8E are compared, the user can
easily verify that the D range is different but the gain is the
same between the case where the D-range-oriented setting is
selected and the case where the S/N-oriented setting is selected,
at the same exposure index EI. The D range is 1600% in the case
where the D-range-oriented setting is selected, whereas the D range
is 200% in the case where the S/N-oriented setting is selected. The
user can easily verify that the signal is amplified by eight times
in the gamma in the D-range-oriented setting as compared with the
S/N-oriented setting. In this case, the D range is expanded, but
the image quality is degraded because the S/N is decreased from the
S/N at the time when the signal is amplified to eight times by the
gain in the preceding stage.
As described above, when the display control processing according
to the present exemplary embodiment is adopted, the exposure
conditions corresponding to intention of the user are effectively
displayed. This enables the user to easily recognize a difference
of the image quality depending on the combination of the gain and
the D range, etc.
In the present exemplary embodiment, the configuration in which the
D range is displayed as the value representing signal amplification
in the gamma has been described. However, the configuration is not
limited thereto. For example, magnification with respect to a
reference D range may be displayed. In this case, .times.1 may be
displayed when the D range is 200%, and .times.2 may be displayed
when the D range is 400%. Both of the D range and the magnification
with respect to the reference D range may be displayed.
A third exemplary embodiment is described. In the above-described
first and second exemplary embodiments, the example has been
described in which the combination of the transmittance of the ND
filter and the amplification factor of the signal is changed based
on whether the D-range-oriented setting is selected. In the present
exemplary embodiment, an example is to be described in which the
user selects a desired D range and the combination of the
transmittance of the ND filter and the amplification factor of the
signal is changed based on the selected D range. Description of a
configuration of the imaging apparatus according to the present
exemplary embodiment is omitted because the configuration is
substantially the same as the configuration of the above-described
first exemplary embodiment, and description is given with the same
reference numerals.
FIG. 9 is a flowchart illustrating processing to determine the
transmittance of the ND filter 104, the gain, and the gamma
correction characteristics according to the present exemplary
embodiment of the present disclosure. The flowchart illustrated in
FIG. 9 is started when the imaging apparatus 100 is turned on, when
the imaging mode is changed, or at optional timing based on manual
operation by the user.
In step S901, the system control unit 50 detects
previously-selected D range. It is assumed that the D range is
selected at optional timing. In the present exemplary embodiment,
it is assumed that the D range is previously selected by the user
with reference to the menu screen, etc., before the processing in
step S901 is executed. In the present exemplary embodiment, any of
200%, 400%, 800%, and 1600% is selectable as the D range.
In step S902, the system control unit 50 selects the combination of
the transmittance of the ND filter and the amplification factor of
the signal, based on the previously-detected selected D range. FIG.
10 is a diagram illustrating the combination of the transmittance
of the ND filter and the amplification factor based on the D range
according to the present exemplary embodiment of the present
disclosure. As illustrated in FIG. 10, for example, when the D
range of 200% is selected, the transmittance of the ND filter is
changed at the amplification factor of one time, and the
amplification factor is set to one time at the exposure index EI of
the wide range (EI 12 to 100). Likewise, when the D range of 400%,
800%, or 1600% is selected, the transmittance of the ND filter is
changed at the amplification factor of two times, four times, or
eight times, respectively, and the amplification factor is set to
two times, four times, or eight times with the exposure index EI of
the wide range. Processing in subsequent steps S903 to S905 are the
same as the processing in steps S304 to S306 in the above-described
first exemplary embodiment. Therefore, description of the
processing is omitted.
As described above, the imaging apparatus according to the present
exemplary embodiment can set the combination (allocation) of the
transmittance of the ND filter and the amplification factor of the
signal at each exposure index EI so as to achieve the selected D
range with the exposure index EI of the wide range, based on the
optionally-selected D range. This configuration makes it possible
to set the various kinds of imaging conditions to acquire an image
with quality reflecting intention of the user while preventing
operability from being complicated when the transmittance of the ND
filter and the amplification factor of the signal are changed in
conjunction with each other in response to operation by the
user.
Although the exemplary embodiments of the present disclosure have
been described, the present disclosure is not limited to these
exemplary embodiments, and various modifications and alternations
can be performed within the scope of the present disclosure. For
example, in the above-described exemplary embodiments, the
configuration has been described in which the setting such as the
D-range-oriented setting and the S/N-oriented setting is selectable
and the combination (allocation) of the exposure conditions at the
exposure index EI is changed based on the setting. However, the
configuration is not limited thereto. For example, a configuration
is adoptable in which a setting other than the D-range-oriented
setting and the S/N-oriented setting is selectable and the
combination of the amplification factor and the transmittance of
the ND filter at the exposure index EI is changed based on the
setting.
In the above-described exemplary embodiments, the configuration has
been described in which total four densities from 0 stop to 3 stops
(one of them is transparent with transmittance of substantially
100%) are provided as the transmittance of the ND filter 104.
However, the configuration is not limited thereto. For example,
transmittance other than the transmittance described above may be
provided as the density of the ND filter 104, and the number of
stops of the transmittance of the ND filter 104 is not limited.
In the above-described exemplary embodiments, the case where the ND
filter 104 is a turret optical filter member has been described.
However, the ND filter is not limited thereto. For example, a
so-called gradation type in which density is varied depending on a
position in one filter, or a configuration in which a plurality of
filters with the same density is provided in an optical path and
intended density is achieved by a combination of insertion/removal
of the plurality of filters to the optical path may be adopted as
the ND filter. As the ND filter 104, a light transmittance variable
device (so-called variable ND filter), light transmittance of which
is electrically controllable, such as a liquid crystal device and
an organic electrochromic (EC) device may be adopted.
Other Embodiments
Embodiment(s) of the present disclosure can also be realized by a
computer of a system or apparatus that reads out and executes
computer executable instructions (e.g., one or more programs)
recorded on a storage medium (which may also be referred to more
fully as a `non-transitory computer-readable storage medium`) to
perform the functions of one or more of the above-described
embodiment(s) and/or that includes one or more circuits (e.g.,
application specific integrated circuit (ASIC)) for performing the
functions of one or more of the above-described embodiment(s), and
by a method performed by the computer of the system or apparatus
by, for example, reading out and executing the computer executable
instructions from the storage medium to perform the functions of
one or more of the above-described embodiment(s) and/or controlling
the one or more circuits to perform the functions of one or more of
the above-described embodiment(s). The computer may comprise one or
more processors (e.g., central processing unit (CPU), micro
processing unit (MPU)) and may include a network of separate
computers or separate processors to read out and execute the
computer executable instructions. The computer executable
instructions may be provided to the computer, for example, from a
network or the storage medium. The storage medium may include, for
example, one or more of a hard disk, a random-access memory (RAM),
a read only memory (ROM), a storage of distributed computing
systems, an optical disk (such as a compact disc (CD), digital
versatile disc (DVD), or Blu-ray Disc (BD).TM.), a flash memory
device, a memory card, and the like.
While the present disclosure has been described with reference to
exemplary embodiments, it is to be understood that the disclosure
is not limited to the disclosed exemplary embodiments. The scope of
the following claims is to be accorded the broadest interpretation
so as to encompass all such modifications and equivalent structures
and functions.
This application claims the benefit of Japanese Patent Application
No. 2018-065510, filed Mar. 29, 2018, which is hereby incorporated
by reference herein in its entirety.
* * * * *